Recent automobiles and vehicles have been built with on-board safety systems which include radar technologies for detecting a location of an object or target with respect to the vehicle so that a driver or collision-avoidance device can react accordingly. A radar system includes a transmitter for sending out a source signal and a receiver for receiving an echo or reflection of the source signal from the target. The received signal is sampled at a selected sampling frequency and the sampled data points of the received signal are entered into a Fast Fourier Transform (FFT) in order to determine a frequency of the returning signal. A range or relative velocity of the target with respect to the vehicle can be determined from this frequency.
The frequency resolution in such radar systems is limited due to the discrete nature of the FFT. Such frequency resolution is a function of a sampling frequency and a number of samples of the received signal. One way to increase accuracy is to take more samples. This however increases the length of the FFT, which increase the number of computations need to perform the FFT, often requiring a prohibitively large number of computations. Additionally, the FFT often produces frequency sidelobes which are considered aberrations. Increasing the length of the FFT without increasing the sample frequency creates higher sidelobes, leading to higher noise levels. Thus, any improvement in accuracy that results from increasing FFT length comes with a corresponding reduction in signal quality. Accordingly, it is desirable to provide a method for improving radar accuracy without increasing a length of FFTs.